Metco 444

[KevGarty]

Hi All,

Been a while since I posted anything.

We have an application that requires Metco 444 sprayed with a spec of:

Porosity - < 7.5%
Hardness - 80 - 88 HRT

We have sprayed a few samples but cant quite get under the 7.5% porosity. Would anyone be willing to share some parameters that would meet the spec above? We have a lab here to carry out Micro's etc but just looking to speed up the process

Thanks in advance

Kev

[Lemster68]

What spray process and torch are you using? What are the parameters that you have tried already?

[KevGarty]

What spray process and torch are you using?  What are the parameters that you have tried already?

Using FST AP50 with 9MB gun

Argon                45 NLPM
H2                     9 NLPM
AMPS                 550
Spray Distance    5"
Nozzle                GH
Feed Rate           60g/min

We are getting around 8 - 9% but hardness is coming in at 73 HRT. Im hoping if we can get the porosity down 1 - 2% our hardness will increase with the more dense coating

[Vadim Verlotski]

It is difficult to give advice without a cross-section, but a possible cause of increased porosity can be too low particle velocities. To increase particle speed you need to increase gas consumption.

[Lemster68]

I don't have the spraying tables for the 9MB, only 3MB. The flow rates are similar, it calls out 500 amps and 64-70 volts. The really striking difference I notice is that they (metco) call for 189g/min powder feed rate.
I also meant to ask if you are measuring 15, 30 or 45T? According to the Metco spec, it has vickers hardness of 250, converting to 15HRT, you could see the hardness that is required, but with the higher testing loads, not too likely.